I. Field of the Invention
The present invention relates generally to the field of mapping and ablation using steerable vascular catheters. The invention is particularly directed to recording and ablation catheter systems applicable to create continuous linear lesions in any cardiac chamber.
II. Discussion of the Related Art
Steerable catheter systems of several types have been devised. Such devices can be inserted into blood vessels or similar bodily areas and their distal ends navigated through the tortuous vascular path to reach areas of the body normally inaccessible without surgery. Catheters of the steerable or self-navigating type, having distal electroded sections for monitoring parts of the body, such as for electrically mapping the heart by receiving and transmitting electrical signals related to the operation of that organ to recording signal processing and display devices are also known. The ability to successfully record impulses or signals and from them electrically map cardiac chambers and valves using flexible catheters having steerable electroded tips has further led to the development of techniques for transcatheter ablation of cardiac tissues that have been identified as the pathways that enable cardiac arrhythmias. This technique has emerged as one of the most important advances in cardiac electrophysiology. Its goal is to destroy the arrhythmogenic tissue without compromising the mechanical or muscular integrity of the cardiac tissues and vessels.
Not long ago, for example, many patients with Wolff-Parkinson-White syndrome or ventricular tachycardia were forced to undergo surgical dissection of the arrhythmogenic tissue followed by a painful and prolonged recovery. Introduction of the transcatheter approach has dramatically reduced the suffering and cost of definitive treatment for many cardiac arrhythmias.
The general approach to this procedure initially preferably utilized high energy direct current delivered to the catheter poles, for example, to disrupt the A-V node condition and even to create a complete heart block by ablating the His bundle. More recently, however, radio frequency has replaced high energy direct current as the preferred primary source of energy and the transcatheter approach for cardiac ablation has become an accepted and common procedure and has been used increasingly as the primary mode of treating cardiac arrhythmias. Transcatheter cardiac tissue ablation is more fully discussed in Avitall et al, xe2x80x9cPhysics and Engineering of Transcatheter Tissue Ablationxe2x80x9d, JACC, Volume 22, No. 3:921-32. The rapid clinical acceptance of this procedure and the proliferation of physicians engaged in transcatheter tissue ablation has mandated the development of improved steerable catheter devices.
Other common cardiac arrhythmias untreatable except with medication, and more recently, surgery, involve atrial fibrillation and flutter. These conditions, in fact, are the most common rhythm disturbances in human beings. For example, approximately 1% of the population of the United States, i.e., more than 2.5 million people, depends on medication to control this condition. These irregular heart rhythms can reach rates of 180 beats/minute or more. The resulting loss of blood flow due to incomplete atrial contractions along with a rapid heart rate can lead to shortness of breath, dizziness, limited physical endurance, chest pains, in patients with coronary heart disease, and other related problems.
Recently, Dr. Cox et al of Washington University School of Medicine in St. Louis, Mo., have devised a surgical procedure called the Maze and Corridor operation. This procedure is an attempt to restore the normal heart rhythm by segmenting the atrial tissues in a manner that allows the normal heart pacemaker to conduct to the AV node as well as preventing the atrial tissues from sustaining the atrial fibrillation. By cutting the atrial tissue, no electrical activity can be transmitted from one segment to another, thus making the segments too small to be able to sustain the fibrillatory process. The approach, while successful, has the same drawbacks as other previous surgical approaches with respect to the recovery of the patient. This represents another area of cardiac arrhythmic treatment where a more benign approach, i.e., without invasive surgery, would represent a definite advance.
In this regard, as with certain other arrhythmia conditions, electrical decoupling of tissues by heating the tissues with radio frequency (RF) energy, microwave energy, laser energy, freezing and sonication, represent possible alternative approaches. Heating tissues above 55xc2x0 C. is known to cause permanent cellular injury, making the cells electrically silent. It has been found that segmenting tissues by creating continuous linear lesions via ablation in the atria mimics some aspects of the maze and corridor procedure. The most important aspect of these lesions is their transmural and continuous character; otherwise, segmenting the heart and preventing atrial fibrillation would not be possible. However, it is possible that limited division of tissues within the right atrium may prevent atrial fibrillation in some patients. Furthermore, segmenting a corridor between the sinus node and the AV node will maintain physiological control of heart rate despite the fibrillation of the atrial tissues.
Present steerable catheter systems, while successful in addressing many internal cardiac areas, have not been so successful in treating atrial fibrillation, for example, because they have not been able to sustain contact with certain surface areas of the atrial chambers without great difficulty. In this regard, prior devices have failed to successfully create the necessary linear lesions via ablation to achieve the desired segmentation. The provision of a recording and ablation catheter system that can successfully treat atrial fibrillation and flutter and other conditions as by making creation of continuous linear lesions in the relevant chamber easier would represent a definite advance in the treatment of this condition.
Accordingly, it is a primary object of the invention to provide an improved catheter, easily deployed and maneuvered to contact desired inner wall surfaces of the any cardiac chamber and sustain contact so that linear lesions can be produced as required.
Another object is to provide multi-electrode working catheter shapes that are easily deployed from sheaths or main catheters once the desired chamber is reached.
An additional object of the invention is to provide such catheter shapes capable of being readily modified to address internal surfaces of varying contour in a linear manner.
Yet another object of the invention is to provide a method of readily mapping and ablating in an atrial chamber.
Still another object of the invention is to provide an improved multi-electrode mapping and ablation catheter for deployment in an atrial chamber by accessing one atrial chamber from the other atrial chamber through the atrial septum.
Yet still another object of the invention is to provide an improved multi-electrode mapping and ablation catheter for deployment in the left atrial chamber that accesses the left atrial chamber via the inferior or superior vena cava, right atrial chamber and the atrial septum.
A further object of the invention is to provide an improved multi-electrode mapping and ablation catheter for deployment in the-left atrial chamber capable of aligning multiple electrodes in any disposition with reference to the wall of that chamber.
A still further object of the invention is to provide a multi-electrode mapping or ablation catheter for deployment in an atrial chamber by accessing the atrial chamber via the aorta.
A yet still further object of the invention is to provide a multi-electrode mapping or ablation catheter for deployment in the left atrial chamber by accessing the left atrial chamber via the aorta and that is capable of ablating a linear lesion of any disposition within the left atrial chamber.
An additional object of the invention is to provide a multi-electrode mapping and ablation catheter deployable in a heart chamber having a plurality of shape controlling devices associated with the deployed system.
Yet an additional object of the invention is to provide a multi-electrode ablation catheter with integral electrode cooling.
Another object of the invention is to provide a deployable mapping and ablation catheter for creating linear lesions in the form of a deployable ribbon loop device.
Yet another object of the invention is to provide an over the wire and a fixed wire multi-electrode mapping and ablation device with relative rotation control.
Other objects and advantages of the invention will become apparent to those skilled in the art in accordance with the descriptions and Figures of this specification.
By means of the present invention, there is provided an array of readily controlled arcuate distal working catheter shapes that form the distal portion of an inner catheter carried by an outer catheter or sheath. The catheters may also-be in the form of ribbon like structure which can be displayed from a sheath to form symmetric or asymmetric loop configurations. The working catheter sections are easily deployed to contact the inner wall surface of any cardiac chamber in a manner that allows them to contour the endocardial surface and enables easy recording or mapping of impulses and thereafter facilitates sustained contact so that linear lesions can be produced from an array of mapping and ablation electrode devices serially spaced along the working catheter shape using the electric heating or radio frequency ablation energy.
The inner catheter is provided with a distal electroded section known as the working catheter section and is inserted through or carried within a lumen of a main vascular catheter or sheath and the working catheter section of the inner catheter is designed to be deployed from the main catheter or sheath once the desired chamber is entered. The main catheter or sheath is provided with an opening at or near the distal end from which the distal portion of the inner catheter or working catheter section is caused to emerge. Using any of several posturing techniques, the working catheter section may be caused to assume any of several deployed shapes, the control of which may be independent of or with reference to the slidable attachment of one or both ends of the working catheter section to an axially displaceable guidewire or other catheter mounted element.
While certain configurations may favor one or the other, it is contemplated that the working catheter of the invention be deployable and fully effective in any heart chamber including either atrial chamber. It is further contemplated that the working catheter section or electroded distal section be one which can access either atrial or ventricular chamber and embodiments are provided for using more than one access route. In this manner, the left atrial chamber, for example, may be accessed via the arterial system through the aorta, the left ventricle and the mitral valve; or through the venous system through either vena cava (the use of the inferior vena cava is illustrated in the Figures) and thereafter piercing the atrial septum to access the left atrial chamber. Once the chamber of interest has been entered in the manner desired, the electroded portion or section which may conveniently be called the working catheter section may be deployed and maneuvered into the desired pattern of contact with the chamber wall. Both mapping and ablation procedures may be combined or achieved singularly using the special deployment and electrode configurations of the invention.
It is important that control of the disposition or posture of the working catheter within the chamber to be treated be made as easy as possible so that the desired alignment at the ablation site can be achieved in the shortest time. Another important aspect of the invention is that the working catheter be able to be controlled so as to sustain an electrode position until ablation is accomplished.
Positioning may also be assisted in certain embodiments by providing additional control devices. In catheters designed to operate slidably over a guidewire, a locking system may be provided in any of several forms to optionally prevent rotation of the distal portion of the catheter relative to the guidewire. In other self-guiding embodiments, the distal end may be permanently fixed to a control wire.
If desired, the ablation catheter may be provided with an auxiliary cooling system to prevent overheating of the tissue adjacent or abutting ablation electrodes after they have been energized. This system flushes desired electrodes with infused saline from an encased movable internal tube through cooling effusion ports provided tube which can be aligned with pores or ports provided in the working catheter and in the electrodes themselves which can be connected with a source of fluid coolant.
The working catheter of the invention may be deployed independently of or may include one or more rider devices which slidably thread over a wire member, which may be the guidewire, and which cooperate with stops limiting travel of at least one of the rider members such that adjustable arcuate forms are assumed by the section intermediate the rider members as their relative separation distance is modulated. A linear or non-linear semi-rigid tube guide member may also be used in conjunction with the guidewire in posturing the working catheter. Additional control elements may be attached along the working catheter between electrodes to provide additional shape modification. In another alternate embodiment, a right- or left-handed loop shape is assumed by the specialty shaped working catheter upon deployment. One or more radiopaque markers may also be provided to assist in positioning and orienting the system.